The present invention relates to an arrangement for a gas urbine for use in gas supply pipe systems particularly in long distance gas transmission lines for supplying gas to low pressure end consumers.
In today's long distance gas piping systems particularly natural gas is conducted over long distances of over thousand kilometers to the end consumer for domestic or industrial heating purposes. In order to be able to transport the gas over such long distances at the least possible losses, it is highly compressed to typically 80 bar and above. In order to feed the gas into the low pressure duct systems of the end consumer with substantially lower safety provisions, the gas pressure must be reduced possibly in several expansion stages arranged in series.
In each expansion stage, a part of the energy stored in the compressed gas is released. For economical reasons, it has not been particularly attractive to try to regain the energy released in the final expansion stages in the long distance piping system between local centers (for example, community gas plants) and the final end users (for example, private gas heating systems for domestic use) and to utilize it, (for example, to generate electricity). The reason for omitting such utilization resides in the high investment and maintenance costs for present gas turbine generators including the necessary safety systems which are not in an economically reasonable relation to the advantages that can be obtained by such local electrical power generation.
EP 000 438 discloses a gas expansion turbine in a gas supply system including a motor generator with a shaft provided with a bladed-turbine wheel.
It is the object of the present invention to provide a turbine plant which is simple, compact, and adequate from a safety and from an economical point of view for decompressing the gas at the end stages of long distance gas transmission lines whereby the energy released by the gas expansion can be converted to electrical energy.